The beacons are being lit at 22:00 local time in the Commonwealth and British overseas territories - those in the UK, Channel Islands and Isle of Man will be set alight between 22:00 and 22:30 BST.

Ticket-holders entered the palace gardens - where teams of helpers handed out picnic hampers created by celebrity chef Heston Blumenthal and royal chef Mark Flanagan - to the accompaniment of a steel band.

"We have chilled country garden soup, Scottish smoked salmon, all kinds of bread, jubilee chicken, cheese, chutney and three cakes.

"The only thing is I don't drink champagne."

Despite some rain on an overcast day, picnickers enjoyed the feast on blankets to the sounds of a string quartet playing classical music.

Picnickers included Paula and Terry McLaughlin, from Hampshire

There was confusion earlier as picnic-goers tried to enter palace grounds at Constitution Hill.

"The guards thought we needed the fancy card inviting you to the palace - but it wasn't needed after all," said Donna Hughes, 30, from mid-Wales.

"We only need ID and our tickets. Now we are through the barriers but we all have to join another queue - it's a bit ridiculous."

Some 10,000 winners of a public ballot and 2,000 VIPs are at the palace for the picnic and concert, which is due to begin at 19:30 BST (18:30 GMT).

The event, which will be broadcast by the BBC, also includes Robbie Williams, Ed Sheeran, JLS, Kylie Minogue, Sir Tom Jones, Jessie J, Annie Lennox and Madness.

Joe Butler, 25, who has travelled down from Sheffield, told the BBC News website he was looking forward to seeing artists from different generations.

"Like my granddad said to me before I left - 'say hello to Shirley Bassey'.

"And you know what, it's really nice to be proud to be British for once - you see lots of Americans with flags but not usually us."

Those without tickets have gathered on The Mall nearby where, despite room becoming tight, the atmosphere remained persistently polite and good-natured.

Paul Spencer, 42, an electrician from Shropshire, said he wanted his two sons, Daniel, five, and Jamie, three to know their country's history.

"They probably won't see this again in their lifetime," he added.

Flagsellers on The Mall, meanwhile, have complained of disappointing sales.

"We definitely haven't sold as many as the last royal celebration - probably because all the papers are giving them away. We can only try."

Monday's celebrations follow Sunday's spectacular River Thames pageant which attracted hundreds of thousands of rain-soaked people to watch the flotilla of 1,000 vessels as street parties took place across the country.

Met Police Commissioner Bernard Hogan-Howe said there had been "absolutely no problems".

"It seems to have gone really well - we had one-and-a half-million people out yesterday and made just 10 arrests so that is not bad," he added.

Thousands of people are expected in central London later to watch the concert on the big screens, which are also located in St James's Park, Hyde Park and Trafalgar Square.

The Prince of Wales, Duke and Duchess of Cambridge and Prince Harry will join the Queen at the concert.